The DLL low water level limiter works in conjunction with the Igema DP111 or DP121 level probe or the DP114 probe on the basis of the conductive fill level method of measurement whereby the electric conductivity of the water medium is used. The conductivity of the medium is measured in µS/cm. For the secure functioning of this method of measurement a minimum conductivity of the substance to be measured is required.
The conductive method of measurement makes two statements: electrode submerged or electrode uncovered or switch point reached or not reached. Before installation the electrode must be brought to the measure at which the switching procedure is to be used, e.g. for switching off burner and interrupting the safety circuit.
The evaluation device can supply one or two limiter probes, which can be fitted in the boiler, with power and evaluate their signals. The serial numbers of the probes used must be entered in the evaluation device so that the evaluator can communicate with these probes.
With the aid of the measurement data received from the probe electronics the evaluation device determines the current water level (electrode submerged / electrode uncovered) in the boiler. If all conditions for correct operation are met, the safety chain for the steam generator is enabled (burner can switch on). On detection (has fallen below minimum level) the relay output “pre-alarm” is switched on immediately and the LED “FAILURE” starts to flash. Should this state be present for longer than the alarm delay time set, the relays of the safety chain will be switched off (safe operation mode) and the LED “FAILURE” remains permanently lit.
In the event of a fault (e.g. broken cable, probe defective, ...) the safety chain is switched of immediately.
Safe operating mode during which the relay contacts of the device go into rest position, corresponds at the same time to the de-energised state of the evaluation device.